RE: Kurzweill Contact PCNB lower board has 6 notes that do not repsond despite cleaning and all new rubber contacts. Wiring harness is good. Diodes on dead notes are good. I can not find bad traces!
Any suggestions as to how to track this phantom down?
Did you try this…with a #2 pencil (if you have a #2 Soft pencil) even better. Drawing slightly on the contact board contacts, this would be all the contacts that effect the sound of the key that isn’t working. Mine had 4 contacts for each key… two for the sound and 2 for the hammer-velocity sensor. You want to leave a small amount of lead from the pencil on each contact…then reattaching the soft rubber contacts strip correctly and retry to see if it works!
I did this on my Fatar 88 key which had 8-10 intermittent keys not working and now it works totally fine - no issues for the past 2-3 weeks of use.
You may also find a YouTube video or a couple of write ups on the internet for this.
I think also that some loosened screws on the key contacts circuit boards might cause symptoms of silent keys or soft, staticy sounding key strokes. Yesterday I had that on top octave of my Korg that I was reassembling after a part replacement. Uniformly tightening all the screws found 3 that were still slightly loose on that end. Snugging those up without over-tightening immediately restored those keys and notes to normal for me.